The present disclosure relates to aircraft environmental control systems. More specifically, the present disclosure relates to an environmental control system with air cycle machine shutoff valves.
Air cycle machines are used in environmental control systems in aircraft to condition air for delivery to an aircraft cabin. Conditioned air is air at a temperature, pressure, and humidity desirable for aircraft passenger comfort and safety. At or near ground level, the ambient air temperature and/or humidity is often sufficiently high that the air must be cooled as part of the conditioning process before being delivered to the aircraft cabin. At flight altitude, ambient air is often far cooler than desired, but at such a low pressure that it must be compressed to an acceptable pressure as part of the conditioning process. Compressing ambient air at flight altitude heats the resulting pressurized air sufficiently that it must be cooled, even if the initial ambient air temperature is very low. Thus, under most conditions, heat must be removed from air by the air cycle machine before the air is delivered to the aircraft cabin.
Air cycle machines that are used in environmental control systems typically include a fan section, a compressor section, and one or more turbine sections. When either the bearings supporting the rotors or the rotors in either the compressor section or the turbine sections fail, particulate from rotor run can be released into the airstream that is being delivered to the cabin and the cockpit. This can cause a smell in the cabin and the cockpit that can cause the aircraft to make an emergency landing in order to investigate the source of the smell. This causes significant delay and cost to get each passenger to their destination via an alternate route, and it also causes significant anxiety for the passengers and crew induced by the declared emergency.